Conventionally, a rare earth phosphovanadate phosphor has been known in which a host crystal is represented by Ln(P, V)O4 (where Ln represents at least one element selected from the group consisting of Sc, Y, La, Gd, and Lu). For example, Ln(P, V)O4 that does not contain other ions as an activator functions as a blue phosphor, and Ln(P, V)O4 (Eu3+-activated rare earth phosphovanadate phosphor) that contains at least Eu3+ ions as an activator functions as a red phosphor (see, for example, Patent Documents 1 to 3 and Non-Patent Document 1).
As a typical example of the rare earth phosphovanadate phosphor, there may be given a Y(P, V)O4:Eu3+ red phosphor (hereinafter, referred to as “YPV”), and the practical application of the YPV to a fluorescent lamp, a PDP, and the like is under consideration.
Conventionally, a rare earth phosphovanadate phosphor that has been put into practical use for an electronic device is produced by a general solid phase reaction, and is produced by reacting a phosphor material to which an alkali metal compound or a boron compound has been added as a flux at a firing temperature of 1,050 to 1,600° C. Conventionally, a flux to be used for the production of the rare earth phosphovanadate phosphor is added to a phosphor material without considering the mixed amounts of a vanadium atom, a phosphorus atom, and an yttrium atom, and the amount of the flux to be added merely is selected appropriately so that emission characteristics of a phosphor become maximum experimentally.
A phosphor produced by a conventional production method using a flux generally is a particle group in which primary particles having an irregular shape flocculate. The primary particles generally exhibit a shape of a polyhedron (for example, a prismatic shape, a needle shape, a cubic shape, a rectangular solid) having a smooth particle surface without concave portions.
There is known a rare earth phosphovanadate phosphor produced by, for example, a spray-pyrolysis method involving heating liquid droplets of a solution (material solution) containing constituent elements of the phosphor to perform pyrolysis synthesis, besides those produced by the solid phase reaction. A phosphor produced by the spray-pyrolysis method is known to become phosphor particles in a spherical outer shape having substantially irregular surface unevenness.